River Pebble (Quartzite/Chert)

Physical Properties

Hardness: 7 (Mohs scale), Color: Creamy white with tan/grey patterns, Luster: Waxy to vitreous when wet/polished, Structure: Microcrystalline, Cleavage: None/Conchoidal fracture

Formation & Geological History

Formed from the metamorphism of quartz-rich sandstone or through silica precipitation. Smooth shape is the result of mechanical weathering in an aquatic environment over years or decades.

Uses & Applications

Landscape decoration, aquarium gravel, tumbling for hobbyists, and industrial abrasive.

Geological Facts

The rounded shape is caused by saltation, where the rock bounces along a riverbed, grinding its edges down. These are among the most common geological finds worldwide.

Field Identification & Locations

Identify by its hardness (will scratch glass), smooth surface, and lack of visible individual grains. Found in riverbeds, glacial deposits, and beaches.

Identified on: 4/15/2026

Mode: Standard